Disruption of egg production by triclabendazole-resistant Fasciola hepatica following treatment with a commercial preparation of myrrh (Mirazid)

Mohamed M.O. Abdelaal, Gerard P. Brennan, Robert E.B. Hanna, Ahmed Abdel-Aziz, Ian Fairweather

An in vitro study has been carried out to monitor changes to the female reproductive system in adult triclabendazole (TCBZ)-resistant Fasciola hepatica following treatment with a commercial preparation of myrrh ("Mirazid"). Flukes were immersed for 6 h and 24 h in myrrh extract at a concentration of 200 µg/ml, then processed for histological and transmission electron microscope (TEM) examination of the uterus, Mehlis' gland, ovary and vitellaria. Egg production had become abnormal at 6 h post-treatment (pt), with the uterine lumen being filled with free vitelline cells and masses of shell protein material; few eggs were present. At 24 h pt, no eggs were present. Distinct changes to the ovary and Mehlis' gland were only observed after 24 h incubation in Mirazid. The ovary contained numbers of apoptotic oogonia and oocytes. In the Mehlis' gland, the S1 cells were disorganised and the processes from them were vacuolated, although the disruption was not significant. More severe changes were observed in the vitelline cells and follicles. After 6 h incubation in Mirazid, although the gross organisation of the vitelline follicles appeared to be normal, nuclear changes indicative of the early stages of apoptosis were observed in the stem cells and shell protein production by the mature cells had decreased. At 24 h pt, a distinct shift in cell population was evident, with the follicles containing mainly mature cells and spaces were present between the cells. The shell globule clusters in the mature cells were disorganised. In more severely-affected follicles, cells were seen to be breaking down, with karyolytic nuclei and disintegrating cytoplasm. Overall, the results have shown that exposure to Mirazid treatment had a severe impact on egg production by TCBZ-resistant flukes, an effect that was mediated by disruption of the vitelline cells and of the mechanism co-ordinating egg formation in the ootype.